In a retail service station environment, the flow rate of fuel dispensed must be controlled for a variety of reasons and requirements. These include but are not limited to prevention of flow, an initial slow flow rate to verify various internal metrological subsystem functionalities, an unrestricted flow rate mode and/or mode limited to a maximum flow rate as specified by jurisdictional regulatory authorities, and a reduced flow rate prior to transaction completion to effect precise cessation at a predetermined volume or price.
Also, because the fuel has value, there is motive for theft and fraud to occur. For example, one mode of theft involves tampering with the dispenser's proportional control valve to induce the unauthorized flow of fuel. For example, a dishonest user may try to steal fuel by exposing an armature of the control valve and/or impartation of extraneous magnetic field thereto. There is also a need to have better information about the operational status of dispenser components for reasons such as maintenance.
Historically, variable flow rate is effectuated by the modulation of current within an actuating field coil (hereinafter “valve coil”) of the proportional control valve. By modulating or applying current to the valve coil, a mechanical force is produced. This force causes the armature to move the valve into an open position.
However, present fuel dispensing systems that employ proportional control valves have certain limitations. Specifically, the aforementioned current is modulated under the presumption that the proportional valve is mechanically intact and functional, and that the valve outputs a proper mechanical force based on the number of windings in the coil to accomplish a gradated fuel flow. Moreover, the presumption likewise exists that the proportional control valve does not permit fuel flow when it does not receive control signals.
A dishonest user may steal fuel by tampering with the valve coil of a proportional control valve. For example, the dishonest user may remove the valve coil from the armature of the proportional control valve so that, even though control signals are not sent to the proportional control valve, an unauthorized flow of fuel is induced.
Consequently, the ability to mechanically tamper with the proportional valve to induce unauthorized flow exists without notice or validation by the controlling modulation mechanism, or more generally, the electronic controller commanding control of the valve.